THE ZOOLOGIST 



No. 894.— December 15th, 1915. 



OBSERVATIONS ON THE FOREIGN OBJECTS CARRIED 

 BY THE PURPLE-TIPPED SEA-URCHIN. 



By H. N. Milligan, F.Z.S. 



The common Purple-tipped Sea-Urchin {Echinus miliaris) 

 has a well-known habit of carrying various objects, which pre- 

 sumably act as a disguise, upon the upper parts of its body. 

 These objects are usually stones, seaweeds, or shells, but the 

 animal may pick up anything which lies in or close to its path 

 as it creeps along, or which lies near its resting-place. In 

 addition to pebbles and seaweed, I have seen the following 

 materials carried by captive individuals of this Sea-Urchin : a 

 bunch of about fifty eggs of the Sea-Bullhead (Cottus bubalis), a 

 living Ascidia sp., a Tube-Worm (Sabella pavonina) of about 

 seven inches in length, a Hydroid (Sertularia operculata), a living 

 Dog-Periwinkle (Nassa reticulata), a living Dog-Whelk (Purpura 

 lapillus), empty shells of Nassa, Purpura, Rissoa membranacea, 

 Trochus cinerarias, and T. zizyphinus, fragments of the shells 

 of various molluscs, and pieces of the broken test of the Edible 

 Sea-Urchin {Echinus esculentus). 



It seemed to me to be desirable, for reasons which will be 

 mentioned later, to obtain a number of fresh Sea-Urchins, tc 

 keep them under constant observation, to make as far as possible 

 detailed notes of their behaviour, and to keep records of the 

 materials which they picked up. Twelve individuals were taken 

 in a dredge from a part of the estuary at Walton- on-the-Naze 

 (Essex) where there is a bottom of gravel. The long diameters 

 (excluding the spines) of these Sea-Urchins were 10, 15, 19, 21, 

 21, 21, 23, 23, 23, 27, 27, and 39 millimetres respectively. The 

 weights of the three first were 0*7, 1*7, and 4*3 grammes, the 

 Zool. 4th ser. vol. XIX., December, 1915. 2 M 



